Crack at upper rear motor mount

[Vmx51]

I was cleaning up a 79 I just bought , and it looks to me that the upper case is cracked from the upper rear mount over to the sprocket side. Has anyone else seen or heard of this ? Transmission seems to shift fine , have not started or ridden the bike though

 

[ippytattoo]

These motors are notorious for casting flaws that look like cracks, mostly up around the cylinder studs, so it may just be a casting flaw but without pics it is hard to really tell what you are seeing.

 

[Uncle Bryan]

Here's a pic of what ippy is talking about. There's nothing broken here, just funky casting. Can you give us a pic?

 

[Vmx51]

jesus wept , that is atrocious , I will try to take pics of my crack !

 

[angus67]

scrub the hell out of it with friend's tooth brush till sparkly clean. ride around a while. if it leaks oil..........

 

[fredintoon]

- - - I will try to take pics of my crack !

Hi Vmx,
biting the inside of my mouth trying not to respond to this.
Alas, the pain is too much.
To get a good pic, try standing on a mirror.

 

[gggGary]

This however IS bad news...

View attachment 47919

Happens when a stretched chain skips a tooth on a worn out sprocket.
There will be two marks on the bottom of the rib that supports the cover screw.

The round steel is the closed end bearing for the shifter shaft.

Is it repairable? Well, new cases would be a lot simpler...

 

[Vmx51]

Fredintoon , I am also going to take a pic of the engine cases , try to guess which is which !

 

[Vmx51]

Gary , it is definately not like that. I will take a pic after work tomorrow.

 

[Brian902]

Thanks Fred and Vmx you made my Monday!!!

 

[Vmx51]

My "crack" ??

 

[DIRTY DOG]

does it leak oil?? it looks like a crack but could be bad casting also check the mounting bolts,make sure there all all tight also is there a upper mount on it?

 

[gggGary]

I am sure that's not a crack it's a casting mark where two sections of the mold come together. It's visible in my first picture and this one.

 

[Vmx51]

Dirty dog , don't know if it leaks , have not cranked it up yet , all stock motor mounts are intact. , Gary. My crack looks just like yours !

 

[mjpchief]

Identical twins?

 

[Vmx51]

Fredintoon , you are fortunate I exposed the relevant crack first !! The alternative is way more distressing!

 

[fredintoon]

Fredintoon , you are fortunate I exposed the relevant crack first !! The alternative is way more distressing!

Hi Vmx,
thanks for not posting the other photo.
It wouldn't bother a hardy soul like me but some folks who look in on this list are still young and easily shocked.
About the photo of the crankcase casting mark, I trust you are going to clean that bike before you run it.
The thick coating of crud on the drive chain and sprockets will act just like grinding paste.